Preparation

Put butter, sugar, and zest in the bowl of an electric mixer. Mix on medium speed until pale and fluffy, about 3 minutes. Reduce speed to low; slowly mix in flour & salt mixture until just combined.

Divide dough in half. Transfer each half to a piece of parchment paper; shape into logs. Roll in parchment to 1 1/4 inches in diameter, pressing a ruler along edge of parchment at each turn to narrow log and force out air. Transfer in parchment to paper-towel tubes; freeze 1 hour.